Improved Linearization of a high power amplifier to reduce spectral distortions near the saturation area

To mitigate in-band and out-of-band linearity problems due to an Orthogonal Frequency Division Multiplexing (OFDM) signal used on a high power amplifier (PA), we propose to improve a linearization technique called baseband digital predistortion. The new algorithm differently processes the samples depending on their power. Predistortion improvement is studied in simulation on a class A PA and then applied on a 50W peak power GaN PA with a 64QAM OFDM signal. Simulations and measurements show an improvement of the out-of-band linearity performance with very slight in-band linearity degradations and at the same time an improvement of the PA efficiency (until 6%-points for the PA Power Added Efficiency (PAE)). For a 40 dBc ACPR, the use of our improved predistortion increases by 1.3 dB the RMS (Root Mean Square) output power in comparison with classic predistortion.